A lithography process in production of a semiconductor device usually includes a process of applying a solution. Examples of the solution used in the application process may include a resist underlayer film-forming composition as a solution and a resist-forming composition as a solution, in which a polymer and an additive or the like are dissolved in an organic solvent. In recent years, use of a solvent that has low harmfulness to the human body and high safety in the lithography process has been increasingly required. For this reason, use of an organic solvent conventionally used may be avoided, and a usable organic solvent tends to be limited.
For example, N-methyl-2-pyrrolidone and cyclohexanone are known to have high skin permeability, and it is suspected to adversely affect the fetus. Further, cyclohexanone is suspected to be carcinogenic.
When the usable organic solvent is limited, a polymer having high solubility in the limited organic solvent should be selected. Otherwise, a homogeneous solution cannot be prepared, and it is difficult to form a homogeneous film.
Examples of documents about a solution used in the lithography process may include Patent Documents 1 and 2. Patent Document 1 describes an anti-reflective coating-forming composition containing a reaction product of a compound having at least two glycidyl ether structures with an aromatic compound such as hydroxybenzoic acid and naphthalenecarboxylic acid. Patent Document 1 describes that in a synthesis example, an oligomer compound is obtained from a compound having 4 or more glycidyl ether structures and a compound having a hydroxy group and/or a carboxyl group, such as 4-hydroxybenzoic acid. One of the solvents that can be used in the present invention described in Patent Document 1 is propylene glycol monomethyl ether. Patent Document 2 describes a resist underlayer film-forming composition for lithography which contains a solvent and a polymer having a structure obtained by introducing 2,4-dihydroxybenzoic acid through an ester bond and an ether bond. One of the solvents that can be used in the present invention described in Patent Document 2 is propylene glycol monomethyl ether.